Plant Physiology

Daley, Paul F.; Raschke, Klaus; Ball, J. Timothy; Berry, Joseph A.

doi: 10.1104/pp.90.4.1233pmid: 16666912

Abstract The distribution of photosynthetic activity over the area of a leaf and its change with time was determined (at low partial pressure of O2) by recording images of chlorophyll fluorescence during saturating light flashes. Simultaneously, the gas exchange was being measured. Reductions of local fluorescence intensity quantitatively displayed the extent of nonphotochemical quenching; quench coefficients, q N, were computed pixel by pixel. Because rates of photosynthetic electron transport are positively correlated with (1 − q N), computed images of (1 − q N) represented topographies of photosynthetic activity. Following application of abscisic acid to the heterobaric leaves of Xanthium strumarium L., clearly delineated regions varying in nonphotochemical quenching appeared that coincided with areoles formed by minor veins and indicated stomatal closure in groups. 1 Support for the Trapix system was provided by the University of California Program for Analytical Cytology. Work by P. F. D. was performed under U.S. Department of Energy contract W-7405-Eng.-48 to the Lawrence Livermore National Laboratory. J. T. B. held a postdoctoral fellowship at the Botany Department at U.C. Davis. K. R. held a fellowship from the Stiftung Volkswagenwerk. This is C.I.W. Publication 1047. This content is only available as a PDF. © 1989 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Witkowski, Debra A.; Halling, Blaik P.

doi: 10.1104/pp.90.4.1239pmid: 16666913

Abstract The effect of acifluorfen-methyl on tetrapyrrole synthesis in greening chloroplasts of Cucumis sativus was examined. Formation of Mg-proto-porphyrin IX from δ-aminolevulinate was reduced 98% by 10 micromolar acifluorfen-methyl. Conversion of protoporphyrin IX to Mg-protoporphyrin IX was unaffected, but protoporphyrin IX synthesis from δ-aminolevulinate was blocked, indicating a site of inhibition prior to the Mg-chelatase. The enzymic oxidation of protoporphyrinogen IX to protoporphyrin IX was highly sensitive to acifluorfen-methyl, indicating that the site of action of the herbicide is the protoporphyrinogen oxidase. (© 1989 FMC Corporation. All rights reserved.) This content is only available as a PDF. © 1989 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Ursin, Virginia M.; Bradford, Kent J.

doi: 10.1104/pp.90.4.1243pmid: 16666914

Abstract Tomato (Lycopersicon esculentum Mill.) plants heterozygous for the diageotropica (dgt) mutation exhibit a unique phenotype, termed `mottled.' Unlike dgt, mottled individuals grow upright, exhibit normal root branching, and produce normal levels of ethylene in response to applied auxin. Leaves of mottled plants are deformed and reduced in size and are characterized by a mottled appearance on their surfaces with small dark-green islands clustered along the leaf veins. The lack of phenotypic overlap between dgt and mottled may represent interallelic interaction at a locus which influences auxin sensitivity or action in the tomato. 2 Current address: USDA/ARS Plant Gene Expression Center, 800 Buchanan Street, Albany, CA 94710. 1 Supported in part by National Science Foundation grant No. DMB-8408857 and a gift from Beatrice/Hunt-Wesson. This content is only available as a PDF. © 1989 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Meir, Shimon; Riov, Joseph; Philosoph-Hadas, Sonia; Aharoni, Nehemia

doi: 10.1104/pp.90.4.1246pmid: 16666915

Abstract The sucrose-stimulated in vivo hydrolysis of indole-3-acetyl-l-alanine (IAAIa) in tobacco (Nicotiana tabacum L.) leaf discs was confirmed by in vitro analysis of an IAAIa-hydrolyzing enzyme isolated from the same tissue. The enzymic activity could be stimulated by either aging of the tissue or by application of external IAA or sucrose. A combination of the above three treatments yielded maximal activity. 1 Supported by grant No. I-773-84 from BARD, the United States-Israel Binational Agricultural Research and Development Fund. Contribution from the Agricultural Research Organization, the Volcani Center, Bet Dagan, Israel. No. 2540-E, 1988 series. Parts I and II in this series: Plant Physiol (1985) 78: 131-143. This content is only available as a PDF. © 1989 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Azcón-Bieto, Joaquim; Ribas-Carbó, Miquel; González-Meler, Miquel A.; Peñuelas, Josep

doi: 10.1104/pp.90.4.1249pmid: 16666916

Abstract The rate of dark O2 uptake of Elodea canadensis leaves was titrated with either cyanide or sulfide in the presence and in the absence of 5 millimolar salicylhydroxamic acid (SHAM), an inhibitor of the alternative oxidase. The inhibition of O2 uptake by SHAM alone was very small (3-6%), suggesting that actual respiration mainly occurred through the cytochrome pathway. O2 uptake was slightly stimulated by cyanide at concentrations of 50 micromolar or higher, but in the presence of SHAM respiration was strongly suppressed. The effects of sulfide on O2 uptake were similar to those of cyanide, except that the percent stimulation of O2 uptake by sulfide alone was somewhat higher than that of cyanide. However, the estimates of the capacity of the alternative pathway were similar with both inhibitors. Another difference is that maximal inhibition of respiration in the presence of SHAM was observed with lower concentrations of sulfide (50 micromolar) than cyanide (250 micromolar). The results suggest that sulfide can be used as a suitable inhibitor of cytochrome c oxidase in studies with intact plant tissues, and that sulfide does not apparently inhibit the alternative oxidase. This content is only available as a PDF. © 1989 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Staswick, Paul E.

doi: 10.1104/pp.90.4.1252pmid: 16666917

Abstract A temporary vegetative storage protein, composed of similar 25 kilodalton and 27 kilodalton subunits, was found to be abundant in soybean (Glycine max (L.) Herr. var Hobbit) leaves, stems, pods, flower petals, germinated cotyledons, and less abundant in roots, nodules and seeds. Total pod protein was highest at 3 weeks after flowering and declined by 37% within 3 weeks during seed development. During this time the vegetative storage protein declined from 18% to 1.5% of the total pod protein and accounted for 45% of the protein lost from pods. This indicates that the vegetative storage protein makes a significant contribution to the pool of nutrients mobilized from pods for transport to developing seeds. 1 Supported in part by the U.S. Department of Agriculture under grant 87-CRCR-1-2300 from the Competitive Research Grant Office. Paper No. 8864 Journal Series, Nebraska Agricultural Research Division. This content is only available as a PDF. © 1989 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Rees, Carol A. B.; Gullons, Annette M.; Walden, David B.

doi: 10.1104/pp.90.4.1256pmid: 16666918

Abstract Exposure of plumules of intact maize seedlings (Zea mays L.) to S-methyl-N-[(methylcarbamoyl)-oxy]thioacetimidate (methomyl) represses synthesis of several polypeptides normally made under control conditions and induces synthesis of polypeptides similar to maize heat shock polypeptides (HSPs). Three of the methomyl-induced polypeptides (18 kilodaltons) are recognized by antibodies raised against 18 kilodalton maize heat shock polypeptides. 1 Supported by Natural Sciences and Engineering Research Council of Canada Operating and Strategic grants. This content is only available as a PDF. © 1989 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Chansa-Ngavej, Kanjana; Raghavan, V.

doi: 10.1104/pp.90.4.1262pmid: 16666919

Abstract Gametophytes of the fern Onoclea sensibilis grow as filaments in the dark and in red light and become planar in blue light. Pulse-labeling 4-day-old gametophytes with [35S]methionine at different times after transfer to dark, red, and blue light environments revealed higher rates of amino acid uptake and protein synthesis in blue light than in red light or in the dark. Characterization of the extant and newly synthesized soluble proteins by one- and two-dimensional gel electrophoresis showed that the patterns of protein accumulation and synthesis in gametophytes exposed to short periods of red or blue light were qualitatively indistinguishable from those of gametophytes maintained in the dark. However, some striking increases and decreases in the levels of certain polypeptides were noted and these changes were accentuated during continued growth of gametophytes in the different environments. The results show that photomorphogenesis of gametophytes of O. sensibilis is associated with quantitative rather than qualitative changes in the population of mRNAs available for translation. 2 Present address: Department of Microbiology, Faculty of Science, Chulalongkorn University, Bangkok 10500, Thailand. 1 This work was supported in part by grants from Sigma Xi to K. C. This content is only available as a PDF. © 1989 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Babbs, Charles F.; Pham, Jo Ann; Coolbaugh, Ronald C.

doi: 10.1104/pp.90.4.1267pmid: 16666920

Abstract Bipyridinium herbicides, including paraquat and diquat, are believed to act by generating highly reactive, oxygen-centered free radicals within chloroplasts when treated plants are exposed to sunlight. This hypothesis has not yet been confirmed by direct chemical measurements of specific free radicals. We studied paraquat-treated plants using a new method able to detect and quantify formation of highly reactive and deleterious hydroxyl radicals (HO*), in which dimethyl sulfoxide (DMSO) is used as a molecular probe. DMSO is oxidized by HO* to form the stable, nonradical compound, methane sulfinic acid, which can be easily extracted from plant tissue and measured spectrophotometrically. Initial experiments revealed formation of extraordinary numbers of hydroxyl radicals in light-exposed, paraquat + DMSO-treated plants, equivalent at least to the cumulative number of HO* radicals per gram of fresh tissue that would be produced by 10,000 rads of gamma irradiation. This appears to be the greatest production of hydroxyl radicals yet observed in a biological system and is quite sufficient to explain the rapid death of top growth in paraquat-treated plants. 1 This work was supported by a Focused Giving Grant from Johnson & Johnson, and by grant HL-35996 from the National Heart, Lung, and Blood Institute, U.S. Public health Service, Bethesda, MD. This content is only available as a PDF. © 1989 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Lynch, Jonathan; Polito, Vito S.; Läuchli, André

doi: 10.1104/pp.90.4.1271pmid: 16666921

Abstract High concentrations of NaCl immediately elevated cytoplasmic Ca activity in maize (Zea Mays L. cv Pioneer 3377) root protoplasts, as measured with the fluorescent probe Indo-1. The effect of salinity was inhibited by Li pretreatment but restored by inositol, suggesting that phosphoinositides mediate the stress response. 2 Present address: Centro Internacional de Agricultura Tropical (CIAT), AA 6713, Cali, Colombia. 1 Supported in part by a grant from the National Science Foundation (DCB-8514451) to V. S. P. This content is only available as a PDF. © 1989 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)